1. Field of the Invention
The present invention relates to a copying machine capable of automatically copying an image on each side of a copying sheet or a plurality of images on one side of a copying sheet, and in particular an improved control unit for a two-sided/multiple copy conveying unit for conveying a copying sheet with an image formed on one side.
2. Description of the Related Art
A copying machine capable of automatically copying a document image on each side of a copying sheet or a plurality of document images on one side of a copying sheet has been developed in this art. This copying machine comprises a copying section for copying an image corresponding to a document image on a sheet, a stacking section for stacking those imaged sheets from the copying section and a conveying unit which, in the case of a two-sided copy mode, conveys the stacked sheet to the copying section in an "inverted" state and, in the case of a multiple copy mode, conveys the stacked sheet to the copying sheet in an non-inverted fashion.
In the aforementioned copying machine, in the two-sided copy mode, a document image is transferred to one side of the sheet at the copying section and conveyed to the stacking section. Then the imaged sheet is taken out of the stacking section and transferred to the copying section in an "inverted" fashion where, for example, another document image is transferred to that side of the sheet.
In the multiple copying mode, a document image is transferred to a half of one side of the sheet and then conveyed to the stacking section. The stacked sheet is conveyed, in that posture, via the conveying unit to the copying section where, for example, another document image is transferred to the remaining half of the sheet.
For the two-sided copy or multiple copy mode, the sheet which is taken out of the stacking section is once stopped at the conveying unit. The sheet thus stopped is responsive to the copying operation of the copying section to be transferred to the copying section. In the copying machine, however, when a plurality of copying sheets are imaged in a continuous copying mode, if the sheet which is taken out of the stacking section is jammed or caught at the location of the conveying unit, the copying operation is stopped until the cause of the jamming is removed. When, in this case, a start-to-copy instruction is issued from an operation panel in the copying machine after the jammed sheet has been removed, the succeeding sheet is taken out of the stacking section and, in this way, a copying operation is started.
In this way, after the interruption of the copying section, the sheet is being held in the stacking section, leaving a long distance from the stacking section to the copying section. For this reason, a long time is taken from the picking up of the sheet from the stacking section subsequent to the issuance of the start-to-copy instruction to the conveyance of the sheet to the copying section. It takes a long time to start a copying operation at the location of the copying section.